It is known that the increasingly widespread use of vehicles powered partly or entirely by means of electric power, for example vehicles with electric energy accumulators, poses the problem of managing in an intelligent manner recharging of the accumulators, preventing simultaneous requests for recharging from exceeding the supply capacity of an electric power supply network (grid), thus resulting in collapse of the network or impeding total or partial provision of the service.
In the case of inadequate power provision, the accumulator may not be sufficiently charged to be able to meet the user's needs at the time of use.
At the same time, requesting electric power during network load peak times is very disadvantageous for the user, since the cost of electric energy increases in line with the demand (during peak periods).
Methods for programming recharging of an accumulator for an electric vehicle, which envisage reading a residual charge level L of the accumulator, so that recharging may be delayed if need be, thereby reducing costs, are known. In other words, if the accumulator is connected to the supply network at a time when the cost of the energy is high and if the residual charge level L of the accumulator is not low, for example at 70%, recharging may be delayed by means of a timer which postpones it so that it is carried out in an economically more advantageous time band.
However, these methods have a number of drawbacks and limitations.
Firstly, they are not applicable on a large scale since, in order to read the residual charge level L of the accumulator, it is necessary to access the accumulator control system situated in the vehicle, which may vary depending on the model of the accumulator or on the vehicle on which it is mounted. Therefore, it is not a simple task to provide a device which is able to read indifferently the accumulators mounted on the various rechargeable vehicles which are in circulation or to install such a device at users' homes, where the accumulator is connected. Moreover, the device might not be compatible with accumulator models which have not yet been introduced onto the market.
Furthermore, even if the aforementioned interfaces are known and the abovementioned complex device is installed, it is not possible to avoid simultaneous requests for recharging from causing a network overload, thereby making it impossible to satisfy all the requests. On other hand, by attempting to reduce the costs for the user, the simultaneous recharging demand during the low consumption time bands may increase, thereby adversely affecting the supply network.
Furthermore, delaying recharging by means of a timer may prevent the accumulator from being completely charged for use.
Finally, the known methods, since they do not take into account the local state of the supply network, do not allow optimum use of renewable energy, for example photovoltaic energy, produced locally, for example at the premises where recharging of the accumulator is performed.
FIG. 1 is a graph showing the charged state of the accumulator, during recharging, as a function of the time, in a known system where charging starts immediately after connection of the accumulator to the electrical network, without reference to economic, tariff-related or electric network load aspects.
The continuous line in the graph indicates the charged state of the accumulator (y axis) as a function of the time (x axis). The broken line indicates the state of the vehicle charger performing charging between T0 and T1 and terminating charging after T1. The price of the energy (dotted line) is not taken into account in this known recharging system.
FIG. 2 is a graph showing the charged state of the accumulator, during recharging, again as a function of the time, in another known system where charging starts after a predefined period of inactivity. This system is useful for considering time bands in which the price of the energy is advantageous, for example low-cost two-hour tariffs. However, this system is limited by the fact that no check is carried out as to the load state of the supply network and the effect of accumulator recharging on the network load state. As indicated by the dotted line in FIG. 2, the charging system with timer is programmed to start charging at the time when the price of the energy is lower or decreasing.
US 2013/0024035 discloses a power supply system including a centralized power controller to control energy flow from a plurality of loads in a building through a monitor unit, the load further including an electric vehicle remotely connected by a plug in station.
The technical problem at the basis of the present invention is to devise a method and device for programming energy flow between the grid and an accumulator of a rechargeable vehicle which is able to reduce the recharging costs for the user but at the same time optimize use of the electric power supply network, without employing complex electronic devices designed ad hoc for the accumulators or for different models of electric vehicle, thus ensuring that the accumulator is substantially charged for subsequent use of the rechargeable vehicle, with the maximum economic advantage for the user and least stress on the network, overcoming the disadvantages and drawbacks which hitherto limit the recharging methods of the prior art.